Assessment of comparative effectiveness of treatment is essential to achieve optimal quality of care [1-2]. Quality of care in healthcare is a multifaceted issue that involves factors related to patient, provider, health care system, community and environment [1-16]. Disparities exist in the quality of prostate cancer care across geographic regions, hospitals, age and racial and ethnic groups [17-23], including treatment variability among comparable patients [17-19, 24-27]. The objective of our study is to analyze the complex interplay of personal factors, clinical factors, provider factors and their relationship with variation in quality of care and heterogeneity of treatment among men with prostate cancer (localized or advanced). Specific aims are: (1): To assess the contribution of provider (hospital and physician) characteristics in the observed disparities (race/ethnicity and disability status) in process of care (type of treatment, time to treatment and diagnostic procedures), and outcomes (short-term and long-term), among prostate cancer patients; (2) To assess the contribution of patient and provider characteristics in the heterogeneous treatment effects among prostate cancer patients; (3) To assess the contribution of continuity of care to the disparity in quality of care (process of care and outcomes) and the heterogeneous treatment effects among prostate cancer patients. To accomplish these aims, we propose a retrospective cohort control design study using the SEER-Medicare linked data. All African American, Asian, Hispanic, and Caucasian men, diagnosed with prostate cancer between 1995 and 2012 (n=282,487) will be identified and followed retrospectively for one year pre-diagnosis and up to fifteen years post-diagnosis. Physician and hospital characteristics will be determined by linkage to the American Medical Association (AMA) and the American Hospital Association (AHA) annual survey, respectively. Our main comparators are various treatments for localized or advanced prostate cancer. We will use multilevel modeling approach. First, we will study the association of hospital characteristics with racial and ethnic disparity in process of care and outcomes. Next, we will analyze the contribution made by physician characteristics to racial and ethnic disparity in process of care and outcomes. Finally, we will investigate the role played by continuity of care in the observed racial and ethnic disparity in process of care and outcomes. We will use propensity score and instrumental variable approaches to minimize measured and unmeasured biases. Our study proposes a novel systems approach for analyzing the complex interplay of provider characteristics and their relationship with racial and ethnic disparities in process of care and outcomes among prostate cancer patients. The study results will aid in development of micro and macro level treatment, care and payment policies to address disparity.